An elephant has a mass of 156,000 kg and a volume of 6 kL. What is the elephant's density?
The numbers are not realistic! But see below....
Density is simply mass per unit volume.
Typical units are
1 cubic metre is equivalent to 1000 litres, so units of "thousands of litres" (kl) and units of cubic metres are numerically identical.
So the mass is 156,000 kg, and the volume is 6
The density is therefore 156,000/6 = 26,000
In reality, this is an unrealistic figure though. The density of water is 1000
So whoever set you this question needs to use some slightly more realistic numbers, but you can see the methodology anyway.